pub fn new_birthday_probability(n: u32) -> f64 {
    if n < 2 {
        return 0.0;
    }
    let mut probability = 1.0;
    let days = 365;
    for i in 0..n {
        probability *= (days - i) as f64 / days as f64;
    }

    let res = 1.0 - probability;
    (res * 10000.0).round() / 10000.0
}
